Sex hormone influence on hepatitis in young male A/JCr mice infected with Helicobacter hepaticus

Helicobacter hepaticus infection induces chronic hepatitis and fibrosis in male BALB/c mice via the activation of NF-κB, Stat3, and MAPK signaling pathways

BACKGROUND

It has been documented that Helicobacter hepaticus (H hepaticus) infection is linked to chronic hepatitis and liver cancer. However, our understanding of the molecular mechanisms underlying progression of the H hepaticus-induced hepatic inflammation to cellular hepatocarcinoma is still limited.

MATERIALS AND METHODS

In our study, male BALB/c mice were infected by H hepaticus for 8, 12, 16, 20, and 24 weeks. Histopathology, H hepaticus colonization dynamics, select signaling pathways, and expression of key inflammatory cytokines in the liver were examined.

RESULTS

We found that H hepaticus was detectible in feces of mice at 7 days postinfection (DPI) by PCR, but it was not detected in the livers by PCR until 8 weeks postinfection (WPI). In addition, abundance of colonic and hepatic H hepaticus was progressively increased over the infection duration. H hepaticus-induced hepatic inflammation and fibrosis were aggravated over the infection duration, and necrosis or cirrhosis developed in the infected liver at 24 WPI H hepaticus infection increased levels of alanine aminotransferase and aspartate aminotransferase. Moreover, mRNA levels of Il-6 and Tnf-α were significantly elevated in the livers of H hepaticus-infected mice compared to uninfected control from 8 WPI to 24 WPI. Furthermore, Stat3, nuclear factor-κB (p65), and MAPK (Erk1/2 and p38) were activated by H hepaticus infection.

CONCLUSIONS

These data demonstrated that male BALB/c mice can be used as a new mouse model of H hepaticus-induced liver diseases and that the H hepaticus-induced liver injury is triggered by NF-κB, Jak-Stat, and MAPK signaling pathways.

Sex hormone affects the severity of non-alcoholic steatohepatitis through the MyD88-dependent IL-6 signaling pathway

Recent research has shown that the occurrence of gender disparity in liver cancer associated with sex differences in MyD88-dependent IL-6 production, but the role of this signaling pathway in sex differences of non-alcoholic steatohepatitis (NASH) remains unknown. To investigate the effects of sex hormone-specific intervention on pathology and progression of NASH, and on the inflammatory TLR-MyD88-IL-6 signaling pathway NASH was modeled in C57/BL6 mice by feeding a methionine and choline-deficient (MCD) diet for 4 weeks. Male mice were subjected to sex hormone-related interventions such as orchidectomy, and orchidectomy combined with administration of either testosterone propionate or estradiol benzoate. Next, the degree of non-alcoholic fatty liver disease activity score (NAS), serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and the expression level of MyD88 and IL-6, were compared between these groups. Males developed more serious inflammatory problems and had a higher NAS than the females. Sex-specific intervention in male mice by orchidectomy reduced NAS, ALT, and AST, and the expression level of MyD88 and IL-6. But administration of exogenous androgen had no influence on either NAS or the expression of ALT, AST, MyD88, and IL-6. On the other hand, exogenous estrogen could alleviate the pathological damage caused by NASH, as well as reduce NAS, ALT and AST, and the expression of MyD88 and IL-6. The result show different sex hormone-related interventions affected the severity of NASH, possibly by modulating the level of sex hormones and regulating the TLR-MyD88-IL-6 signaling pathway.

Prolactin prevents hepatocellular carcinoma by restricting innate immune activation of c-Myc in mice

Women are more resistant to hepatocellular carcinoma (HCC) than men despite equal exposure to major risk factors, such as hepatitis B or C virus infection. Female resistance is hormone-dependent, as evidenced by the sharp increase in HCC incidence in postmenopausal women who do not take hormone replacement therapy. In rodent models sex-dimorphic HCC phenotypes are pituitary-dependent, suggesting that sex hormones act via the gonadal-hypophyseal axis. We found that the estrogen-responsive pituitary hormone prolactin (PRL), signaling through hepatocyte-predominant short-form prolactin receptors (PRLR-S), constrained TNF receptor-associated factor (TRAF)-dependent innate immune responses invoked by IL-1β, TNF-α, and LPS/Toll-like receptor 4 (TLR4), but not TRIF-dependent poly(I:C)/TLR3. PRL ubiquitinated and accelerated poststimulatory decay of a "trafasome" comprised of IRAK1, TRAF6, and MAP3K proteins, abrogating downstream activation of c-Myc-interacting pathways, including PI3K/AKT, mTORC1, p38 MAPK, and NF-κB. Consistent with this finding, we documented exaggerated male liver responses to immune stimuli in mice and humans. Tumor promotion through, but regulation above, the level of c-Myc was demonstrated by sex-independent HCC eruption in Alb-Myc transgenic mice. PRL deficiency accelerated liver carcinogenesis in Prl(-/-) mice of both sexes. Conversely, pharmacologic PRL mobilization using the dopamine D2 receptor antagonist domperidone prevented HCC in tumor-prone C3H/HeN males. Viewed together, our results demonstrate that PRL constrains tumor-promoting liver inflammation by inhibiting MAP3K-dependent activation of c-Myc at the level of the trafasome. PRL-targeted therapy may hold promise for reducing the burden of liver cancer in high-risk men and women.

Androgen receptor roles in hepatocellular carcinoma, fatty liver, cirrhosis and hepatitis

Androgen/androgen receptor (AR) signaling plays important roles in normal liver function and in progression of liver diseases. In studies of noncancerous liver diseases, AR knockout mouse models of liver disease have revealed that androgen/AR signaling suppresses the development of steatosis, virus-related hepatitis, and cirrhosis. In addition, studies have shown that targeting AR in bone marrow-derived mesenchymal stem cells (BM-MSCs) improves their self-renewal and migration potentials, thereby increasing the efficacy of BM-MSC transplantation as a way to control the progression of cirrhosis. Androgen/AR signaling is known to be involved in the initiation of carcinogen- or hepatitis B virus-related hepatocellular carcinoma (HCC). However, studies have demonstrated that AR, rather than androgen, plays the dominant role in cancer initiation. Therefore, targeting AR might be an appropriate therapy for patients with early-stage HCC. In contrast, androgen/AR signaling has been shown to suppress metastasis of HCC in patients with late-stage disease. In addition, there is evidence that therapy comprising Sorafenib and agents that enhance the functional expression of AR may suppress the progression of late-stage HCC.

Distance burning: how gut microbes promote extraintestinal cancers

Gut microbes play a major role in carcinogenesis of the gastrointestinal tract. We and others have shown in mouse models that colonic bacteria also influence the development of extraintestinal cancers including hepatocellular and mammary carcinomas. Microbes such as Helicobacter hepaticus invoke a proinflammatory microenvironment in the lower bowel that may extend to distant organs, often in the absence of histologically evident inflammation. Innate immunity plays a crucial role in the promotion of liver cancer and other systemic diseases by gut microbes. Additional mechanisms include type 1 adaptive immunity, altered metabolism, and oxidative stress. Emerging links between host genetics, gut microbes, inflammatory bowel disease and colorectal cancer also may prove useful for the correlation of specific bacterial populations with extraintestinal neoplasms. Interruption of deleterious host-microbe networks through judicious use of antibiotics and targeted molecular therapies may help reduce the incidence of liver, breast, and other human cancers.

The struggle within: microbial influences on colorectal cancer

Recently, an unprecedented effort has been directed at understanding the interplay between chronic inflammation and development of cancer, with the case of inflammatory bowel disease (IBD)-associated colorectal cancer at the forefront of this research endeavor. The last decade has been particularly fertile, with the discovery of numerous innovative paradigms linking various inflammatory, proliferative, and innate and adaptive immune signaling pathways to the development of colorectal cancer. Because of the preponderant role of the intestinal microbiota in the initiation and progression of IBD, recent efforts have been directed at understanding the relationship between bacteria and colorectal cancer. The microbiota and its collective genome, the microbiome, form a diverse and complex ecological community that profoundly impacts intestinal homeostasis and disease states. This review will discuss the differential influence of the microbiota on the development of IBD-associated colorectal cancer and highlight the role of innate immune sensor-dependent as well as -independent mechanisms in this pathology.

Gut microbes define liver cancer risk in mice exposed to chemical and viral transgenic hepatocarcinogens

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) frequently results from synergism between chemical and infectious liver carcinogens. Worldwide, the highest incidence of HCC is in regions endemic for the foodborne contaminant aflatoxin B1 (AFB1) and hepatitis B virus (HBV) infection. Recently, gut microbes have been implicated in multisystemic diseases including obesity and diabetes. Here, the hypothesis that specific intestinal bacteria promote liver cancer was tested in chemical and viral transgenic mouse models.

METHODS

Helicobacter-free C3H/HeN mice were inoculated with AFB1 and/or Helicobacter hepaticus. The incidence, multiplicity and surface area of liver tumours were quantitated at 40 weeks. Molecular pathways involved in tumourigenesis were analysed by microarray, quantitative real-time PCR, liquid chromatography/mass spectrometry, ELISA, western blot and immunohistochemistry. In a separate experiment, C57BL/6 FL-N/35 mice harbouring a full-length hepatitis C virus (HCV) transgene were crossed with C3H/HeN mice and cancer rates compared between offspring with and without H hepaticus.

RESULTS

Intestinal colonisation by H hepaticus was sufficient to promote aflatoxin- and HCV transgene-induced HCC. Neither bacterial translocation to the liver nor induction of hepatitis was necessary. From its preferred niche in the intestinal mucus layer, H hepaticus activated nuclear factor-kappaB (NF-kappaB)-regulated networks associated with innate and T helper 1 (Th1)-type adaptive immunity both in the lower bowel and liver. Biomarkers indicative of tumour progression included hepatocyte turnover, Wnt/beta-catenin activation and oxidative injury with decreased phagocytic clearance of damaged cells.

CONCLUSIONS

Enteric microbiota define HCC risk in mice exposed to carcinogenic chemicals or hepatitis virus transgenes. These results have implications for human liver cancer risk assessment and prevention.

Hepatocellular carcinoma: prevalence and molecular pathogenesis of Helicobacter spp

Helicobacter pylori infection is one of the most common chronic bacterial infections in humans. The association of other Helicobacter spp. with extragastric diseases in animals is well established, and a role of these bacteria in human liver disease is becoming clearer. Several case-control studies have reported possible associations of Helicobacter spp. with various liver diseases, including hepatocellular carcinoma, which is the fifth most common type of carcinoma among men worldwide, and the eighth most common among women. Thus, it is important to understand molecular mechanisms that may lead to hepatotoxicity or hepatocellular dysfunction in which Helicobacter spp. may play a role in inducing malignant transformation of liver cells.

Helicobacter spp. other than Helicobacter pylori

Non-H. pylori Helicobacter species (NHPHS) are associated with several important human and animal diseases. In the past year research into this group of bacteria has continued to gain attention, and novel species have been described in new niches owing to improvements in detection methods. Polymerase chain reaction and/or sequencing remain the gold standard for the detection of this genus. New insights into the pathogenesis of the NHPHS in hepatobiliary, gastric, and intestinal diseases were gained. In particular, data revealed interaction between hepatic steatosis and infectious hepatitis in the development of hepatocellular carcinoma. Evidence of an association between hepatitis C virus and Helicobacter spp. in hepatocarcinoma development was also provided; and male sex hormone signaling appeared to influence infectious hepatitis induced by Helicobacter hepaticus. More findings support an association between Helicobacter heilmannii and gastric adenocarcinoma; and in mice, mucins MUC4 and MUC5 but not MUC1 influence the colonization and pathogenesis of Helicobacter felis. Data indicated that the roles of the adaptive immune system in H. hepaticus-induced intestinal tumorigenesis are different in the small and large intestines, and environmental factors, such as bile acids may modulate H. hepaticus carcinogenic potential. New reports in the prevention and eradication of NHPHS showed a protective response against Helicobacter suis induced by vaccine administration, and a successful cross-foster rederivation method successfully eradicated Helicobacter spp. from contaminated mice litters. Overall, the studies provided insights into the pathophysiology of Helicobacter species other than Helicobacter pylori.

Effects of Helicobacter infection on research: the case for eradication of Helicobacter from rodent research colonies

Infection of mouse colonies with Helicobacter spp. has become an increasing concern for the research community. Although Helicobacter infection may cause clinical disease, investigators may be unaware that their laboratory mice are infected because the pathology of Helicobacter species is host-dependent and may not be recognized clinically. The effects of Helicobacter infections are not limited to the gastrointestinal system and can affect reproduction, the development of cancers in gastrointestinal organs and remote organs such as the breast, responses to vaccines, and other areas of research. The data we present in this review show clearly that unintentional Helicobacter infection has the potential to significantly interfere with the reliability of research studies based on murine models. Therefore, frequent screening of rodent research colonies for Helicobacter spp. and the eradication of these pathogens should be key goals of the research community.